Kangjoo Kim

Tracing the sources of nitrate in the Han River watershed in Korea, using δ15N-NO3− and δ18O-NO3− values

The dissolved nitrate concentrations and their nitrogen and oxygen isotopic ratios were analyzed in seasonal samples from Koreas Han River to ascertain the seasonal and spatial variations of dissolved nitrate and its possible sources. Nitrate concentrations in the South Han River (SHR) were much higher than those in the North Han River (NHR), probably because of the more extensive distribution of agricultural fields, residential areas and animal farms in the SHR drainage basin. The nitrogen isotopic composition of dissolved nitrate indicates that nitrate-nitrogen (NO(3)(-)-N) is derived mainly from atmospheric deposition and/or soil organic matter in the NHR but comes principally from manure or sewage, with only a minor contribution from atmospheric deposition or soil organic matter, in the SHR. The oxygen isotopic compositions of dissolved nitrate suggest that most atmospheric nitrate undergoes microbial nitrification before entering the river.

Co-contamination of arsenic and fluoride in the groundwater of unconsolidated aquifers under reducing environments.

The co-contamination of arsenic (As) and fluoride (F(-)) in shallow aquifers is frequently observed worldwide, and the correlations between those contaminants are different according to the redox conditions. This study geochemically explores the reasons for the co-contamination and for the redox-dependent correlations by investigating the groundwater of an alluvial aquifer in Korea. Geochemical signatures of the groundwater in the study area show that the As concentrations are enriched by the reductive dissolution of Fe-(hydr)oxides, and the correlations between As and F(-) concentrations are poor comparatively to those observed in the oxidizing aquifers. However, F(-) concentrations are strongly dependent on pH. Desorption/adsorption experiments using raw soils and citrate-bicarbonate-dithionite treated soils indicated that Fe-(hydr)oxides are the important As and F(-) hosts causing the co-contamination phenomenon. The weaker correlation between F(-) and As in reducing aquifers is likely to be associated with sulfate reduction, which removes As from groundwater without changing the F(-) concentration.

Veterinary antibiotics contamination in water, sediment, and soil near a swine manure composting facility

Antibiotics have been commonly used to prevent animal diseases and promote livestock productivity. However, its release into the surrounding environments leads to ecological disturbance and risks to human health. This study was conducted to monitor the occurrence and seasonal variations of antibiotics in water, sediment, and soil close to a swine manure composting facility, Korea. Various types of antibiotics such as tetracyclines (TCs) including tetracycline, chlortetracycline, and oxytetracycline, and sulfonamides (SAs) including sulfamethazine, sulfamethoxazole, and sulfathiazole were measured by the high-performance liquid chromatography-tandem mass spectrometry via a solid-phase extraction. In the results it was identified that the variations of measured antibiotics’ concentrations in water, sediment, and soil are depending on the season. The observed concentration levels of TCs were higher in winter than in summer season, indicating that the low temperature is a parameter attributing to interruption of its degradation in water, sediment, and soil. The concentration levels of SAs were significantly higher than those of TCs and in general, all measured antibiotics’ concentrations were also in general higher in Korea when compared to those in other countries. The long-term monitoring of antibiotics’ residues in aquatic and terrestrial environments is necessary.

Hydrochemical and multivariate statistical interpretations of spatial controls of nitrate concentrations in a shallow alluvial aquifer around oxbow lakes (Osong area, central Korea)

Hydrochemical and multivariate statistical interpretations of 16 physicochemical parameters of 45 groundwater samples from a riverside alluvial aquifer underneath an agricultural area in Osong, central Korea, were performed in this study to understand the spatial controls of nitrate concentrations in terms of biogeochemical processes occurring near oxbow lakes within a fluvial plain. Nitrate concentrations in groundwater showed a large variability from 0.1 to 190.6 mg/L (mean=35.0 mg/L) with significantly lower values near oxbow lakes. The evaluation of hydrochemical data indicated that the groundwater chemistry (especially, degree of nitrate contamination) is mainly controlled by two competing processes: 1) agricultural contamination and 2) redox processes. In addition, results of factorial kriging, consisting of two steps (i.e., co-regionalization and factor analysis), reliably showed a spatial control of the concentrations of nitrate and other redox-sensitive species; in particular, significant denitrification was observed restrictedly near oxbow lakes. The results of this study indicate that sub-oxic conditions in an alluvial groundwater system are developed geologically and geochemically in and near oxbow lakes, which can effectively enhance the natural attenuation of nitrate before the groundwater discharges to nearby streams. This study also demonstrates the usefulness of multivariate statistical analysis in groundwater study as a supplementary tool for interpretation of complex hydrochemical data sets.

Tracing the geographical origin of beefs being circulated in Korean markets based on stable isotopes.

We have examined the carbon, nitrogen and oxygen isotopic compositions of American, Mexican, Australian, New Zealand and Korean beefs, which are currently being circulated in Korean markets, to check whether stable isotope ratios can identify their country of origin. Each beef exhibited statistically distinct isotopic compositions, especially in oxygen and carbon, because of the different isotopic compositions of their water and cattle feeds. Nevertheless, their isotopic compositions still showed some overlap, especially among USA, Australian, and Korean beefs, which sometimes resulted in significant misidentification when a single isotope was considered. However, the discrimination was generally successful when both the carbon and the oxygen isotopes were used.

A review of the arsenic concentration in paddy rice from the perspective of geoscience

Along with contaminated drinking water, arsenic (As) contamination in rice has become a global concern as a potential dietary risk to human health. Arsenic naturally occurs in paddy soil and can be increased by irrigating with As-rich groundwater, which may have subsequent impact on rice grains. There have been many studies on As concentration in rice. Some studies have revealed that As concentration in rice depends on the As content in irrigated groundwater and soil, whereas others have shown that various other factors control As solubility, bioavailability and uptake in the soil-rhizosphere-plant system. This review discusses the major factors controlling As behavior in the soil-rhizosphere-plant system and the current status of As contamination in paddy rice from different parts of the world. Understanding this aspect is crucial for minimizing As toxicity in rice plants.

Nitrate contamination of alluvial groundwaters in the Nakdong River basin, Korea

Nitrate (NO3−) is one of the most serious pollutants encountered in shallow groundwater system. To secure the sustainable development of alluvial groundwaters, therefore, it is important to understand the source(s) and extent of nitrate pollution. In this paper, we have studied the hydrogeochemistry of alluvial groundwaters (n=137) that were collected from irrigation and domestic wells in the Wolha, Daesan, and Yongdang areas on the border of a lower reach of Nakdong River, Korea. The analyzed nitrate concentrations range widely from below the detection limit to 383.4 mg/L NO3− (median=55.4 mg/L). About 58% of the examined samples have the nitrate concentrations exceeding the Korean Drinking Water Standard (44.3 mg/L NO3−) Agricultural practices in the study sites are the main cause of serious nitrate pollution and control the hydrochemical facies change from Ca−HCO3 type toward Ca−NO3(CI) type for the waters. However, the hydrochemical facies change also reflects the water-rock interaction and redox reactions in aquifer. The correlations between nitrate concentration and other physicochemical data can be effectively used to understand the hydrochemical evolution and origins of major ions in waters. The δ15N values of nitrate in waters (n=18) indicate two sources of nitrate pollution: (1) nitrates (δ15N=4.3–6.2‰) originated from synthetic fertilizers applied in agricultural land, and (2) nitrates (δ15N=15.0–19.9‰) from animal manure and human wastes that were discharged from adjacent villages located at hydrogeologically upstream site. Based on the δ15N and nitrate concentration data, we quantitatively evaluate the degree of hydrologic mixing between the two nitrate sources (and corresponding two water bodies), which occurs through local infiltration process along the groundwater flow direction.

Inorganic chemicals in an effluent-dominated stream as indicators for chemical reactions and streamflows

Abstract The chemical behavior of major inorganic ions in the streams of the Mankyung River area (South Korea) was investigated. Mixing with effluent from the Jeonju STP (a municipal sewage treatment plant in Jeonju City) was the most important process in regulating the water chemistry of the streams. The effluent was chemically distinct relative to the stream waters in inorganic composition. Behavior of various ions was evaluated by comparing their concentrations with the concentration of chloride, a conservative chemical species. It was revealed that concentrations of chloride and sulfate, the total concentration of major cations, and electrical conductivity in the stream were controlled only by mixing, indicating their conservative behavior similar to chloride. Alkalinity and concentration of nitrate, however, were regulated by various reactions such as mixing, photosynthesis, respiration, and decomposition of organic matter. Streamflows were estimated by observing chemical composition of the effluent and those of up/downstream waters. Estimated flows based on the conservative chemical parameters were nearly the same as those directly measured using an area–velocity method, indicating the validity of the chemistry-based method.

Current Approaches for Mitigating Acid Mine Drainage

AMD is one of the critical environmental problems that causes acidification and metal contamination of surface and ground water bodies when mine materials and/or over burden-containing metal sulfides are exposed to oxidizing conditions. The best option to limit AMD is early avoidance of sulfide oxidation. Several techniques are available to achieve this. In this paper, we review all of the major methods now used to limit sulfide oxidation. These fall into five categories: (1) physical barriers,(2) bacterial inhibition, (3) chemical passivation, ( 4) electrochemical, and (5) desulfurization.We describe the processes underlying each method by category and then address aspects relating to effectiveness, cost, and environmental impact. This paper may help researchers and environmental engineers to select suitable methods for addressing site-specific AMD problems.Irrespective of the mechanism by which each method works, all share one common feature, i.e., they delay or prevent oxidation. In addition, all have limitations.Physical barriers such as wet or dry cover have retarded sulfide oxidation in several studies; however, both wet and dry barriers exhibit only short-term effectiveness.Wet cover is suitable at specific sites where complete inundation is established, but this approach requires high maintenance costs. When employing dry cover, plastic liners are expensive and rarely used for large volumes of waste. Bactericides can suppress oxidation, but are only effective on fresh tailings and short-lived, and do not serve as a permanent solution to AMD. In addition, application of bactericides may be toxic to aquatic organisms.Encapsulation or passivation of sulfide surfaces (applying organic and/or inorganic coatings) is simple and effective in preventing AMD. Among inorganic coatings,silica is the most promising, stable, acid-resistant and long lasting, as compared to phosphate and other inorganic coatings. Permanganate passivation is also promising because it creates an inert coating on the sulfide surface, but the mechanism by which this method works is still unclear, especially the role of pH. Coatings of Fe-oxyhydroxide, which can be obtained from locally available fly ash are receiving attention because of its low cost, self-healing character, and high cementation capacity. Among organic coatings, lipids and natural compounds such as humic acid appear to be encouraging because they are effective, and have a low environmental impact and cost. Common advantages of organic vs. inorganic coatings are that they work best at low pH and can prevent both chemical and biological oxidation.However, organic coatings are more expensive than inorganic coatings. Furthermore,while organic coatings are effective under laboratory conditions, they often fail under field conditions or require large amounts of reagents to insure effectiveness.Electrochemical cover technology may become a suitable technique to prevent AMD, but the mechanism by which this technique operates is still under investigation.Limitations of this method include the initial capital cost and ongoing costs of anodes and cathodes.Desulfurization is an alternative process for managing large-scale sulfide wastes/tailings. This process can separate sulfide minerals into a low-volume stream, leaving mainly waste with low sulfur content that will be non-acid-generating. The attractiveness of desulfurization is that it is simple and economic.Our review has clearly disclosed that more information is needed for most of the AMD-mitigation techniques available. Silica passivation has shown promise, butmore extensive field-testing is needed to reduce it to commercial viability. Silica is the dominant element in fly ash, and therefore, its use as a low-cost, easily accessible coating should be evaluated. Permanganate passivation also requires further study to understand the role of pH. The secondary formation of Fe-oxyhydroxide minerals from Fe-oxyhydroxides, from the standpoint of their phase transformation,stability and effectiveness, should be assessed over longer experimental periods. All inorganic coatings are designed to inhibit abiotic oxidation of pyrite; however, their effect on biotic pyrite oxidation is not well known and should be further studied.Currently, there is no information available on longer-term field application of organic reagents. Such information is needed to evaluate their lifetime environmental and performance effects. Future studies require spectroscopic analyses of all coating types to achieve a better understanding of their surface chemistry. In addition,a thorough mineralogical and geochemical characterization of waste materialsis essential to understand the acid generating potential, which can indeed help to select better prevention measures.From having performed this review, we have concluded that no single method is technologically mature, although the majority of methods employed are promising for some applications, or at specific sites. Combining techniques can help ac~Ie:eAMD containment in some cases. For example, applying dry cover (e.g., sml) mcombination with liming material or a bactericide, or applying inorganic coatings(e.g., silica) along with organic reagents (e.g., lipids or humic acid) may be moreeffective than utilizing any single technique alone.

Microbial and chemical contamination of groundwater around livestock mortality burial sites in Korea — a review

This review defines and discusses type and fate of microbial contaminants expected to be found in the groundwater around livestock mortality burial pits. Reported results from simulated and actual mortality burial pits indicate that decomposition process of animal carcass requires at least 2 years for completion, generating the leachate with very high concentrations of chemical pollutants. These chemical constituents are likely to provide substrate for bacterial growth and affect microbial population dynamics in the subsurface. Anticipated microbial pollutants are classified into 3 categories. (1) enteric microorganisms including disease causing viruses, (2) bacteria participating in carcass decomposition, such as proteolytic and lipolytic bacteria, and (3) endogenous soil microorganisms. Experimental and field data indicate that pathogenic enteric viruses and bacteria may be able to survive in the animal body and natural environments for extended periods of time when ambient conditions are suitable for their survival. Proteolytic bacteria may affect pathogenicity of avian influenza viruses by controlling their cellular attachment and infiltration. Pathogenic soil bacteria can experience shift in population dynamics, with the introduction of leachate chemicals, from attached bacterial community with limited size to exponentially growing suspended biomass accustomed to the conditions in the groundwater. The possibility of extended survival of various sources of microbial contamination indicates the need to set up a method to properly monitor groundwater contamination to identify the presence of microbial contaminants and their interaction with chemical constituents.